> Using the right codec, they could likely upload a hour of audio in a few hundred kbytes.

But at the same time, you're convinced that you would notice if your phone was slipping out these kilobytes as part of its usual communication?

It seems to me that you've just arbitrarily picked a level of paranoia where you've decided that this can definitely happen with the Alexa, but won't happen with your phone. Your proud paranoia isn't applied consistently.